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SAP HANA - PlanViz and plan cache - Elapsed or CPU time?

Mar 10, 2017 at 01:45 PM

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Hi,

I'd need some clues regarding the time reported by PlanViz (Execution time) and plan cache (TOTAL_EXECUTION_TIME in the HOST_SQL_PLAN_CACHE and M_SQL_PLAN_CACHE system views).

1. The documentation does not clearly state whether it's elapsed time (the real/wall clock time) or CPU time (the total time spent on the queries by CPU).

  • This can make quite a difference when the query execution plan uses multiple threads (which is quite often the case with Hana).
  • I guess that both TOTAL_CURSOR_DURATION and the time reported by PlanViz are CPU usage - but I'm not sure.

2. Is there a way to get the other value?

  • I'd like to know both the CPU and elapsed time, as these two numbers together draw the whole picture (CPU time = resource consumption, elapsed time = the response time experienced by the user).
  • Sometimes the optimization targets on user experience (decrease the response time), but other times you need to decrease the resource consumption (so that the application can scale up with threads). So I definitely need to know both numbers, depending on the actual use case.

Thanks, Ondrej

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